(a) Field of the Invention
The present invention relates to a suspension system for a vehicle and, more particularly, to an active suspension system for a vehicle which assumes an optimal geometrical shape depending on the driving state.
(b) Description of the Related Art
Generally, conventional active control suspension systems are designed to control the roll and pitch of a vehicle body by detecting the same and forcing the vehicle body against the directions of the roll and pitch. To apply such force to the vehicle body, the suspension system requires the use of a high level of energy.
That is, when using hydraulic force, the mechanical energy W of a hydraulic actuator can be calculated using an equation as shown in the following: EQU W=F.multidot.S=.vertline.F.vertline..vertline.S.vertline.Cos.theta.
where, F is the actuator force, S is an actuator stroke, and .theta. is an actuating angle of the actuator with respect to a vertical direction of the vehicle.
In a conventional active suspension system, as is well known, since the hydraulic actuator is disposed in a vertical direction with respect to the vehicle body, a great amount of mechanical energy needs to be exerted by the actuator to support the vehicle body. Even when the actuator is not mechanically operating in a state where no roll and pitch is applied to the vehicle, mechanical energy for supporting the vehicle against outer force is required.
Therefore, to apply such a great amount of mechanical energy, a high capacity hydraulic pump, a highly precise actuator, and various valves are required, complicating the suspension system, enlarging the size of the same as well as increasing manufacturing costs.